Method for preparing acid addition salts of polyacidic basic compounds

ABSTRACT

This invention relates to a method for preparing an acid addition salt of a polyacidic basic compound, or a water adduct having basic site(s) stronger than pyridine. The method comprises reacting the polyacidic basic compound with an acid salt of pyridine. 
     By the present invention, the number of moles of an added acid in the acid addition salt of the polyacidic basic compound can be readily changed to a number suited for the polyacidic basic compound as needed.

TECHNICAL FIELD

This invention relates to a method for preparing an acid addition saltof a polyacidic basic compound or a water adduct of the acid additionsalt, which makes it possible to readily add a desired number of molesof an acid to the polyacidic basic compound.

BACKGROUND ART

Pharmaceutical compositions are well known to have significantdifferences in solubility, oral absorption, drug activity, stability andthe like depending on the kind and crystallized type of their salts,even when they are made of the same ingredient in free form. For thedevelopment of a pharmaceutical composition, it is therefore extremelyimportant to select an ingredient enabling itself to fulfill the mostpreferred conditions, based on the results obtained by makingcomprehensive analysis on the material's characteristics, such aschemical stability, bioavailability and physical stability (the degreeof crystallinity and the degree of hydration), effects on pharmaceuticalproperties (hardness, disintegration property and elution property) andeffects on pharmaceutical capabilities (formability, anticaking propertyand capacity).

Piperazine derivatives, which are categorized into polyacidic basiccompounds and represented typically by2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,are useful as inhibitors against the enzyme (acyl coenzyme A cholesterolacyltransferase, ACAT) that catalyzes the synthesis of cholesterol intoa cholesterol ester (WO 98/54153 Pamphlet).

Inhibition of ACAT is thought to prevent cholesterol absorption throughthe intestinal tract, and also to suppress the secretion ofvery-low-density lipoprotein into blood at the liver, leading to areduction in blood cholesterol. Further, inhibition of ACAT suppressesthe foaming of macrophages in artery walls, so atherosclerosis lesionsare expected to shrink per se. ACAT inhibitors are, therefore, expectedto be applicable for the treatment and prevention of various diseasessuch as hyperlipidemia, arteriosclerosis, cervical and cerebralarteriosclerosis, cerebrovascular accidents, ischemic heart diseases,coronary sclerosis, nephrosclerosis, arteriosclerotic nephrosclerosis,arteriolosclerotic nephrosclerosis, malignant nephrosclerosis, ischemicbowel diseases, acute mesenteric vaso-occlusion, chronic intestinalangina, ischemic colitis, aortic cancer, and arteriosclerosis obliterans(ASO), and numerous researches and developments are now under way.

Among the above-described piperazine derivatives useful as ACATinhibitors,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,for example, has a problem such that it crystallizes in the form of thefree base, but its oral absorption is little well because its crystalsare not uniform and its physical stability and water solubility are toolow.

Solutions to the aforementioned problems have been attempted mainly byadding an acid to such polyacidic basic compounds to improve their oralabsorption or the like and using them as acid addition salts. Forexample,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidecan be substantially improved in water solubility and oral absorption byconverting it into the tetrahydrochloride 2-water adduct with an excessamount of hydrochloric acid.

Nonetheless, it has been pointed out that the number of moles of theadded acid affects the physical properties of the resulting acidaddition salt of the polyacidic basic compound, and that thetetrahydrochloride 2-water adduct cannot avoid a low degree ofcrystallinity in its powder X-ray diffraction analysis; it issusceptible to dehydration and dehydrochlorination in a differentialscanning thermal analysis; and it is also recognized as having highhygroscopicity in a hygroscopicity test. A further problem is alsopresumed in that tableting machines and aluminum sheets may undergometal corrosion due to the residual of the acid used in excess and thestrong acidity of the tetrahydrochloride. This raises concern abouteffects of the metal corrosion on the formulation of a pharmaceuticalpreparation and also on the stability of the pharmaceutical preparation.It is necessary to fully control factors such as drying temperature,vacuum (reduced pressured) level and drying degree upon preparation. Yetit is difficult to efficiently and stably supply such acid additionsalts as active ingredients for pharmaceutical compositions while alwaysproviding them with uniform physical properties.

For the resolution of the above-described problems, it may becontemplated to prepare an acid addition salt with the number of molesof the acid to be added being controlled. However, there is still aproblem in that when hydrochloric acid or the like is used as an acid,it is difficult to accurately measure the amount of the acid in a molenumber desired to be added to 1 mole of a polyacidic basic compound,thereby becoming too hard to easily prepare the acid addition salt ofthe polyacidic basic compound, said salt containing the added acid in adesired number of moles, or a water adduct of the acid addition salt.

Accordingly, there has since been strong demand for a preparation methodmaking it possible to easily adjust the number of moles of an acid in anacid addition salt of a polyacidic basic compound to a number suited forthe polyacidic basic compound as needed.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a preparation methodwhich makes it possible to easily adjust the number of moles of an acidin an acid addition salt of a polyacidic basic compound, to a desirednumber.

With the foregoing circumstances in mind, the present inventorsconducted an extensive investigation. As a result, it has been foundthat by reaction of a polyacidic basic compound with an acid salt ofpyridine, said acid salt being formed from pyridine and an acid, it isreadily possible to prepare an acid addition salt of the polyacidicbasic compound with a desired number of moles of the acid being added tobasic site(s) stronger than pyridine. It has also been found that acidaddition salts of various piperazine derivatives, said acid additionsalts being available from the practice of the above method, forexample,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct has a high degree of crystallinity,has no hygroscopicity, is excellent in thermal stability without beingaccompanied with any substantial weight change by dehydration,dehydrochlorination and/or the like, does not develop the problem ofpolymorphism, and is free from the influence of any residual ofhydrochloric acid, so that said compound is a preferred acid additionsalt and is useful as a pharmaceutical ingredient. Based on thesefindings, the present invention has been completed.

Thus the present invention provides a method for the preparation of anacid addition salt of a polyacidic basic compound having basic site(s)stronger than pyridine or a water adduct of the acid addition salt,which comprises reacting the polyacidic basic compound with an acid saltof pyridine.

The present invention also provides2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, or2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof.

The method of the present invention can easily prepare a salt of apolyacidic basic compound with a desired number of moles of an acidadded thereto. According to this preparation method, it is possible notonly to control the number of moles of an added acid, but also to firmlyprepare an acid addition salt of a polyacidic basic compound which isunstable to the acid.

The use of the acid salt of pyridine relatively weakens the acidity ofthe acid, and substantially lessens the problems of the conventionalmethod such as the decomposition, the formation of impurities and thelike by a localized pH reduction in a system due to the addition or thelike of a strong acid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct.

FIG. 2 shows the results of TG-DSC measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct.

FIG. 3 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidetetrahydrochloride 2-water adduct.

FIG. 4 shows the results of TG-DSC measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidetetrahydrochloride 2-water adduct.

FIG. 5 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedisulfate 1.5-water adduct.

FIG. 6 shows the results of TG-DSC measurements of2-[(4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedisulfate 1.5-water adduct.

FIG. 7 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate 4-water adduct.

FIG. 8 shows the results of TG-DSC measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate 4-water adduct.

FIG. 9 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate.

FIG. 10 shows the results of TG-DSC measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate.

FIG. 11 shows a powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedimaleate.

FIG. 12 shows the results of TG-DSC measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedimaleate.

FIG. 13 and FIG. 14 show a diagram showing the results of TG-DTAmeasurements of2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

FIG. 15 and FIG. 16 show the results of TG-DTA measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its dihydrochloride, respectively.

FIG. 17 and FIG. 18 show the results of TG-DTA measurements of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

FIG. 19 and FIG. 20 show the results of TG-DTA measurements of2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamideand its dihydrochloride, respectively.

FIG. 21 and FIG. 22 show the results of TG-DTA measurements of2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

FIG. 23 and FIG. 24 show the results of TG-DTA measurements of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

BEST MODES FOR CARRYING OUT THE INVENTION

The polyacidic basic compound for use in the present invention is acompound having one or more basic sites stronger than pyridine, and itsexamples include nitrogen-containing compounds having plural ones ofpiperazino groups, tertiary amino groups, secondary amino groups,primary amino groups and the like in the same molecule. Preferred as thepolyacidic basic compound are nitrogen-containing organic compounds,with piperazine derivatives being more preferred.

Preferred as the piperazine derivatives are those represented by thefollowing formula (1):

wherein X represents —NH—, an oxygen atom or a sulfur atom, Y¹, Y² andY³ each independently represent a hydrogen or halogen atom or a loweralkyl or lower haloalkyl group, R¹, R² and R³ each independentlyrepresents a hydrogen or halogen atom or a lower alkyl, lower haloalkyl,lower alkylthio, lower haloalkoxy or lower alkoxyalkoxy group, l denotesan integer of from 1 to 2, m denotes an integer of from 2 to 4, and ndenotes an integer of from 1 to 3. The term “lower” as used herein meansa carbon number of from 1 to 5, with 1 to 3 being particularlypreferred.

More preferred as the piperazine derivatives are those represented bythe following formula (2):

wherein X represents —NH—, an oxygen atom or a sulfur atom, Y¹ and Y²each independently represent a hydrogen or halogen atom or atrifluoromethyl group, R¹ and R² each independently represent a methyl,trifluoromethyl, methylthio, trifluoroethoxy or methoxyethoxy group.Particularly preferred are2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamide,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,and2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide.These compounds can be prepared by the method disclosed WO 98/54153.

The acid salt of pyridine, which is for use in the present invention, isthe salt of pyridine with an inorganic acid or organic acid, and noparticular limitation is imposed on the acid which forms a salt withpyridine. Examples thereof include inorganic acids such as hydrochloricacid, sulfuric acid, nitric acid, phosphoric acid, sulfurous acid,nitrous acid, hydrobromic acid and hydroiodic acid; fatty acids such asacetic acid, butyric acid and stearic acid; polybasic acids such asoxalic acid, maleic acid, succinic acid and fumaric acid;hydroxycarboxylic acids such as citric acid, lactic acid, tartaric acid,malic acid, mandelic acid, salicylic acid, pamoic acid, pantothenic acidand gluconic acid; sulfonic acids such as ethanedisulfonic acid,benzenesulfonic acid, paratoluenesulfonic acid and methanesulfonic acid;acidic amino acids such as glutamic acid and aspartic acid; andtrifluoroacetic acid, and tannic acid.

Preferred examples of the acid include hydrochloric acid, sulfuric acid,maleic acid, fumaric acid, tartaric acid, malic acid, citric acid,methanesulfonic acid and the like, with hydrochloric acid, sulfuric acidand maleic acid being more preferred, with hydrochloric acid beingparticularly preferred.

The acid salt of pyridine may be used no matter whether its form is incrystalline or non-crystalline.

In the preparation of said crystalline acid salt of pyridine, it istheoretically possible to obtain an acid salt of pyridine by reactingpyridine and an acid in equal equivalent amounts. Even so it ispreferred that the reaction be performed by using pyridine in an excessamount relative to the acid in an anhydrous or water-containing organicsolvent, for example, by using pyridine 1.0 to 1.5 times, morepreferably 1.0 to 1.2 times as much as the acid in terms of equivalents.The acid salt of pyridine so formed can be purified by a conventionalcrystallization method making use of a solvent or the like.

When a crystalline acid salt of pyridine is reacted with the polyacidicbasic compound in the present invention, the acid salt of pyridine isused generally in an amount sufficient to supply the acid in the samenumber of moles as the acid to be added to 1 mole of the polyacidicbasic compound. Specifically, the amount of the acid salt of pyridine issubject to the kind and amount of a solvent to be used, and it ispreferred that the acid salt of pyridine be used in an enough amountable to supply the acid 1.0 to 3.0 times, preferably 1.0 to 2.5 times asmuch as the number of moles of the acid to be added.

When the acid addition salt of the polyacidic basic compound is preparedby using a non-crystalline acid salt of pyridine, it is preferred thatthe reaction be performed in an anhydrous or water-containing organicsolvent by adding to the polyacidic basic compound the acid 1.0 to 2.5times, preferably 1.0 to 1.2 times as much as the amount correspondingto the number of moles of the acid to be added to 1 mole of thepolyacidic basic compound and also pyridine 1.0 to 1.5 times inequivalents, preferably 1.0 to 1.2 times in equivalents as much as theamount of the acid to be used.

In a process for the preparation of the acid addition salt of thepolyacidic basic compound, a salt interchange is observed to occurbetween the polyacidic basic compound and the acid salt of pyridine toform the acid addition salt of the polyacidic basic compound, when thepolyacidic basic compound and the acid salt of pyridine in an amountnecessary for the acid to be added are heated and dissolved in anorganic solvent at 0 to 120° C., more preferably at room temperature to100° C., especially preferably at the reflux temperature of the organicsolvent used.

Examples of the organic solvent used in the above process include loweralcohols such as methanol, ethanol and isopropanol; ethers such asdioxane and tetrahydrofuran; and acetone and acetonitrile. Mixedsolvents obtained by adding water to organic solvents are also usable.

No particular limitations are imposed on the kind and amount of thesolvent to be used in the above process. It is nevertheless desirable tosuitably choose the kind and amount of the solvent so that the yield ofthe acid addition salt of the polyacidic basic compound can bemaximized.

The resulting acid addition salt of the polyacidic basic compound or theresulting water adduct of the acid addition salt can be obtained bycollecting precipitated crystals optionally after allowing the reactionmixture to stand for 0.5 to 24 hours under stirring and the reactionproduct to crystallize out.

The acid salt of pyridine of the present invention has an activity toweaken the acidity of the acid employed, so when the free form of thepolyacidic basic compound becomes unstable to the acid, it cansignificantly alleviate problems such as the decomposition of the activeingredient and the formation of impurities due to a localized pHreduction in the system by the addition or the like of the strong acidin the conventional methods.

The preparation method of the present invention is extremelyadvantageous for the preparation of acid addition salts of theabove-described piperazine derivatives, especially2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, and2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof. Namely, no problem isexisting with preparing2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidetetrahydrochloride 2-water adduct, given the use of hydrochloric acid inan excess amount. However, even if there is a need that an amount ofhydrochloric be precisely weighed as in the case of the preparation of amonohydrochloride or a water adduct thereof, it would be extremelydifficult not only to conduct its operation, but also to obtain thedesired uniform hydrochloride or its water adduct.

When preparing2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, and2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, use of a water-containinglower alcohol as an organic solvent is preferred.

In particular,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct obtained as described above has ahigh degree of crystallinity, does not have hygroscopicity, is excellentin thermal stability without any a weight change due to dehydration,dehydrochlorination or the like, has no problem of polymorphism, and isfree from influence by a residual of hydrochloric acid, so this is apreferred acid addition salt.

EXAMPLES

The present invention will hereinafter be described in further detail onthe basis of Examples, although the present invention should not beconstrued as being confined to the following Examples.

Example 1 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-Water Adduct

(1) After heating and dissolving the free base (2.00 kg, 3.98 mol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamideand pyridine hydrochloride (0.92 kg, 7.96 mol) in ethanol (12 L) atreflux temperature, water (20 L) was added dropwise to the reactionmixture at 75 to 87° C. The reaction mixture was allowed to cool down toroom temperature, and was stirred for 1 hour. Precipitated crystals werecollected by filtration. The crystals were washed with water and driedat 80° C. under reduced pressure to obtain2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride water adduct (1.96 kg, 89.0%; found to contain 2% ofethanol from ¹H-NMR) as colorless needles.

(2)2-[4-[2-(Benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride water adduct (1.96 kg) prepared in the procedure (1)was suspended in water (40 L), and at reflux temperature, the solvent(20 L) was distilled off under the environmental pressure. Afterallowing the residue to cool down to room temperature, precipitatedcrystals were collected by filtration, washed with water and dried at80° C. under reduced pressure to obtain the title compound (1.70 kg,84.2%) as colorless needles.

Melting point: 194-196° C.

IR(KBr)cm⁻¹: 3431, 1674, 1625, 1564, 1520.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, s), 2.40 (3H, s), 2.45 (3H, s),2.75-3.75 (14H, m), 6.92 (1H, m), 7.08-7.20 (2H, m), 7.42-7.53 (2H, m),9.38 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₂.HCl.0.9H₂O (in view of 2.84% watercontent as determined by a water content test):

Calculated: C, 49.74; H, 5.95; N, 15.13; Cl, 6.38; S, 17.32

Found: C, 49.97; H, 6.00; N, 15.24; Cl, 6.48; S, 17.26

Referential Example 1 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidetetrahydrochloride 2-Water Adduct

The free base (134.31 g, 0.267 mol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidewas dissolved in methanol (500 mL), followed by the dropwise addition of10% (w/v) hydrogen chloride in methanol (607.6 g, 1.666 mol) over 15minutes under stirring at 0° C. Diethyl ether (700 mL) was added, andthe mixture was left over for 2 hours. Precipitated crystals werecollected by filtration, washed successively with a 1:1 mixed solvent(500 mL) of methanol-diethyl ether and diethyl ether (500 mL), and driedat room temperature for 3 hours under reduced pressure to afford thetitle compound (133.54 g, 73.0%) as colorless crystals.

Melting point: 193-196° C.

IR(KBr)cm⁻¹: 3405, 2922, 1699, 1614, 1564, 1516.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.42 (3H, s), 2.43 (3H, s), 2.46 (3H, s),3.66-3.84 (10H, m), 3.91 (2H, t, J=7.3 Hz), 4.09 (2H, br s), 6.95 (1H,s), 7.33-7.43 (2H, m), 7.63-7.69 (2H, m), 10.16 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₂.4HCl.2H₂O:

Calculated: C, 40.35; H, 5.59; N, 12.28; Cl, 20.71; S, 14.05

Found: C, 40.12; H, 5.83; N, 12.13; Cl, 20.59; S, 14.27

Referential Example 2 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedisulfate 1.5-Water Adduct

Sulfuric acid (purity: 96%, 799.9 mg, 7.83 mmol) was diluted with water(1.5 mL). The free base (1.94 g, 3.86 mmol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidewas added to the above diluted sulfuric acid, and dissolved at roomtemperature.

Ethanol (4.5 mL) was added, and a viscous substance formed was dissolvedunder heat. The solution was stirred at room temperature for 10 minutes,followed by the further addition of ethanol (9 mL). The mixture waschilled under stirring in ice water. Precipitated crystals werecollected by filtration, and heated and dried at 80° C. for 3 hoursunder reduced pressure to afford the title compound (2.64 g, 94.3%) as acolorless powder.

Melting point: 204-208° C.

IR(KBr)cm⁻¹: 3403, 1700, 1617, 1567, 1521.

¹H-NMR (400 MHz, DMSO-d₆, 120° C.) δ: 2.44 (3H, s), 2.46 (3H, s), 2.48(3H, s), 3.05-3.14 (4H, m), 3.26-3.53 (8H, m), 3.60 (2H, m), 6.92 (1H,m), 7.16-7.19 (2H, m), 7.48-7.52 (2H, m), 9.18 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₃.2H₂SO₄.1.5H₂O:

Calculated: C, 38.06; H, 5.14; N, 11.58; S, 22.09

Found: C, 37.99; H, 5.20; N, 11.39; S, 22.27

Referential Example 3 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate 4-Water Adduct

The free base (2.95 g, 5.86 mmol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidewas heated and dissolved at 80° C. for 2 minutes in 1 mol/L sulfuricacid (6 mL, 6.00 mmol). The solution was left over at room temperaturefor 3 days to induce precipitation of crystals. Subsequent todecantation, water (15 mL) was added, crystals were collected byfiltration, successively washed with water (15 mL) and isopropanol (10mL+5 mL), and left over (dried in the air) at room temperature underenvironmental pressure for 24 hours in an open system to afford thetitle compound (3.71 g, 94.1%) as colorless prisms.

Melting point: Unspecified.

IR(KBr)cm⁻¹: 3431, 1674, 1625, 1564, 1520.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.40 (6H, s), 2.45 (3H, s), 2.80-3.72 (14H,m), 6.92 (1H, m), 7.11-7.18 (2H, m), 7.43-7.53 (2H, m), 9.38 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₃.H₂SO₄.4H₂O:

Calculated: C, 41.06; H, 5.99; N, 12.49; S, 19.06

Found: C, 40.92; H, 5.85; N, 12.35; S, 19.07

Referential Example 4 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate

The2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate 4-water adduct (3.25 g, 4.83 mmol), which had been preparedin Referential Example 3, was heated under reflux and dissolved in 97.5%ethanol (120 mL). The solution was left over at room temperature for 3days to induce precipitation of crystals. The crystals were collected byfiltration, washed with ethanol (30 mL+20 mL), and heated and dried at80° C. for 6 hours under reduced pressure to afford the title compound(2.70 g, 93.0%) as colorless fine needles.

Melting point: 170-171° C.

IR(KBr)cm⁻¹: 3431, 1674, 1625, 1564, 1520.

¹H-NMR (400 MHz, DMSO-d₅) δ: 2.40 (6H, s), 2.45 (3H, s), 2.80-3.72 (14H,m), 6.92 (1H, m), 7.11-7.18 (2H, m), 7.43-7.53 (2H, m), 9.38 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₃.H₂SO₄:

Calculated: C, 45.98; H, 5.37; N, 13.99; S, 21.35

Found: C, 45.73; H, 5.40; N, 13.75; S, 21.38

Referential Example 5 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedimaleate

The free base (23.75 g, 47.2 mmol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidewas dissolved in ethanol (200 mL). Maleic acid (11.4 g, 98.2 mol) wasadded and dissolved under heat to prepare a homogeneous solution. Thereaction mixture was concentrated under reduced pressure and the residuewas crystallized from ethanol-ethyl acetate. The crystals were collectedby filtration to afford the title compound (30.95 g, 89.1%) as colorlesscrystals.

Melting point: 127-130° C.

IR(KBr)cm⁻¹: 3424, 1687, 1624, 1576, 1492.

¹H-NMR (400 MHz, DMSO-d₅) δ: 2.43 (3H, s), 2.45 (3H, s), 2.47 (3H, s),2.93-3.00 (4H, m), 3.08-3.17 (4H, m), 3.25 (2H, t, J=6.8 Hz), 3.37 (2H,br s), 3.55 (2H, t, J=6.8 Hz), 6.14 (4H, s), 6.91 (1H, s), 7.13-7.16(2H, m), 7.44-7.50 (2H, m), 9.04 (1H, br s).

Elemental analysis for C₂₃H₃₀N₆OS₃.2C₄H₄O₄ (maleic acid):

Calculated: C, 50.67; H, 5.21; N, 11.44; S, 13.09

Found: C, 50.49; H, 5.37; N, 11.20; S, 13.36

A powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct is illustrated in FIG. 1, and theresults of its TG (thermogravimetric analysis)-DSC (differentialscanning calorimetry) measurements are shown in FIG. 2. Further, apowder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidetetrahydrochloride 2-water adduct is illustrated in FIG. 3, and theresults of its TG-DSC measurements are shown in FIG. 4. A powder X-raydiffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedisulfate 1.5-water adduct is illustrated in FIG. 5, and the results ofits TG-DSC measurements are shown in FIG. 6. A powder X-ray diffractionpattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate 4-water adduct is illustrated in FIG. 7, and the results ofits TG-DSC measurements are shown in FIG. 8. A powder X-ray diffractionpattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonosulfate is illustrated in FIG. 9, and the results of its TG-DSCmeasurements are shown in FIG. 10. A powder X-ray diffraction pattern of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidedimaleate is illustrated in FIG. 11, and the results of its TG-DSCmeasurements are shown in FIG. 12.

TABLE 1 Invention Comparative Examples Hydrochloride HydrochlorideSulfates Maleate Salt Monohydrochloride Tetrahydrochloride DisulfateMonosulfate 0.9-water adduct 2-water adduct 1.5-water adduct 4-wateradduct Monosulfate Dimaleate Solubility mg/mL 0.5 >1000 >1000 5 200 (5when 15 left over) pH of 1% aq. Solution 5.2 (0.05%) 1.97 2.00 3.2(0.5%) 3.2 (0.5%) 2.62 Melting point (° C.) 194-196 193-196 204-208Unspecified 170-171 127-130 Thermal stability 99.2% 98.5% 99.6% 99.4%(Not measured) 93.1% Hygro-scopicity None 10% 10% None 15% 2% PowderX-ray Crystallinity Low crystallinity Low crystallinity CrystallinityLow crystallinity Low crystallinity TG No change until Gradual removalNo change until Decreased 10% at No change until Removal of waterdecomposition of water and HCl decomposition 100° C. and lowerdecomposition of crystallization DSC 1 peak at 1 peak at 2 peaks at 1683 peaks at 95, 168 1 peak at 2 peaks at 117 194° C. 188° C. and 210° C.and 210° C. 172° C. and 137° C. (Note) Thermal stability: The purity ofeach acid addition salt of the polyacidic basic compound stored at 80°C. for 10 days was determined by HPLC measurement relative to its puritybefore the storage with the proviso that the disulfate 1.5-water adductand the dimaleate were stored at 60° C. for 7 days before their storageat 80° C. for 10 days. Hygroscopicity: A weight change of each acidaddition salt was measured after storing it for 4 days under conditionsof 25° C. and 83% relative humidity. TG: Thermogravimetric analysis DSC:Differential scanning calorimetry

As being evident from Table 1,2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride 0.9-water adduct according to the present inventionhad a high degree of crystallinity, had no hygroscopicity, was excellentin thermal stability without any substantial weight change resultingfrom dehydration, dehydrochlorination and/or the like, did not developthe problem of polymorphism, was free from the influence of any residualof hydrochloric acid, and therefore, was a preferred acid addition salt.

Example 2 Preparation of2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride (1) Preparation of1-tert-butoxycarbonyl-4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazine

To a solution of 1-tert-butoxycarbonyl-4-(2-hydroxyethyl)piperazine(7.40 g, 32.13 mmol) in THF (100 mL), triethylamine (4.36 g, 43.09mmol), 4-dimethylaminopyridine (200 mg, 1.64 mmol) and methanesulfonylchloride (7.40 g, 38.76 mmol) were successively added under ice coolingand stirring. The temperature of the reaction mixture was allowed torise to room temperature, at which the reaction mixture was stirred for50 minutes. The reaction mixture was filtered, and the filtrate wasconcentrated under reduced pressure. The residue was dissolved in DMF(200 mL). At room temperature, 5,6-difluoro-2-mercaptobenzimidazole(5.00 g, 26.86 mmol), potassium carbonate (8.64 g, 62.51 mmol) and18-crown-6 (500 mg, 1.92 mmol) were successively added, followed bystirring at 80° C. for 90 minutes. The reaction mixture was concentratedunder reduced pressure, and the residue was purified by columnchromatography on silica gel (silica gel: 200 g; developer:hexane:acetone=8:1→1:1). Crystallization was conducted fromacetone-ethyl ether-hexane to obtain the title compound (7.26 g, yield:680) as colorless crystals.

Melting point: 192.3-193.0° C.

IR(KBr)cm⁻¹: 3061, 2976, 2836, 1672, 1475, 1427.

¹H-NMR (400 MHz, CDCl₃) δ: 1.50 (9H, s), 2.51-2.68 (4H, m), 2.94 (2H, t,J=5.4 Hz), 3.28 (2H, t, J=5.4 Hz), 3.45-3.65 (4H, m), 6.85-7.62 (2H, m).

(2) Preparation of1-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazinetritrifluoroacetate

1-tert-Butoxycarbonyl-4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazine(7.26 g, 18.22 mmol) was added to trifluoroacetic acid (50 mL) over 15minutes under ice cooling and stirring to dissolve the same. Subsequentto stirring for 10 minutes under ice cooling, ether (100 mL) and hexane(100 mL) were added to the reaction mixture and crystals were collectedby filtration. The crystals were recrystallized from ethanol-diethylether to afford the title compound (9.58 g, yield: 82%) as a pale yellowpowder.

Melting point: 141.2-142.9° C.

IR(KBr)cm⁻¹: 3417, 3026, 2749, 2483, 1671, 1484.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.78-3.26 (10H, m), 3.49 (2H, t, J=7.2 Hz),7.51 (2H, t, J=9.0 Hz), 8.76 (2H, m).

(3) Preparation of2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-nitropyridine

2,4-Dichloro-6-methyl-3-nitropyridine (30 g, 144.9 mmol) was dissolvedin 2,2,2-trifluoroethanol (250 mL), followed by the addition ofpotassium carbonate (50 g, 361.8 mmol). The mixture was subjected toheating under reflux for 21 hours. The reaction mixture was extractedwith chloroform-water. The organic layer was washed with a saturatedaqueous solution of sodium chloride (brine), dried over anhydrous sodiumsulfate, and concentrated under reduced pressure to obtain the titlecompound (45.40 g, 94%) as a pale yellow oil.

Melting point: 72.8-73.2° C.

IR(KBr)cm⁻¹: 3432, 3111, 2975, 1610, 1585, 1535.

¹H-NMR (400 MHz, CDCl₃) δ: 2.50 (3H, s), 4.49 (2H, q, J=7.7 Hz), 4.85(2H, q, J=8.3 Hz), 6.53 (1H, s).

Elemental analysis for C₁₀H₈F₆N₂O₄:

Calculated: C, 35.94; H, 2.41; N, 8.38

Found: C, 35.94; H, 2.45; N, 8.49

(4) Preparation of3-amino-2,4-bis(2,2,2-trifluoroethoxy)-6-methylpyridine

2,4-Bis(2,2,2-trifluoroethoxy)-6-methyl-3-nitropyridine (45.00 g, 134.7mmol) was dissolved in isopropanol (300 mL). While stirring the solutionat 80° C., a solution of sodium dithionite (78.00 g, 448.0 mmol) inwater (300 mL) was added, followed by stirring for 15 minutes. Asolution of sodium dithionite (16.50 g, 94.8 mmol) in water (51 mL) wasadded, and the mixture was stirred for 10 minutes. Further, a solutionof sodium dithionite (11.10 g, 63.8 mmol) in water (51 mL) was added,followed by stirring for 10 minutes. A 4 mol/L aqueous solution ofsulfuric acid (201 mL) was added, and the mixture was stirred at 90° C.for 30 minutes. After allowing the reaction mixture to cool down to roomtemperature, 28% aqueous ammonia (310 mL) was added to the reactionmixture in an ice bath, followed by stirring for 30 minutes. The mixturewas extracted with chloroform. The organic layer was washed with brine,dried over anhydrous sodium sulfate, and concentrated under reducedpressure. The residue was recrystallized from hexane to obtain the titlecompound (32.91 g, 80%) as pale yellow needles.

Melting point: 53.5-53.8° C.

IR(KBr)cm⁻¹: 3453, 3314, 2968, 1603, 1505, 1456.

¹H-NMR (400 MHz, CDCl₃) δ: 2.34 (3H, s), 3.66 (2H, br s), 4.39 (2H, q,J=8.0 Hz), 4.79 (2H, q, J=8.6 Hz), 6.35 (1H, s).

Elemental analysis for C₁₀H₁₀F₆N₂O₂.0.55H₂O:

Calculated: C, 38.24; H, 3.56; N, 8.92

Found: C, 37.96; H, 3.19; N, 8.94

(5) Preparation of2-bromo-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide

3-Amino-2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-nitropyridine (42.29g, 139.0 mmol) was dissolved in dichloromethane (600 mL), followed bythe addition of N,N-dimethylaniline (20.46 g, 16.8 mmol). While stirringthe mixture in an ice bath, a solution of bromoacetyl bromide (28.73 g,142.3 mmol) in dichloromethane (100 mL) was added dropwise, and thereaction mixture was stirred at room temperature for 10 minutes. Thereaction mixture was extracted with chloroform-water. The organic layerwas washed with brine, dried over anhydrous sodium sulfate, andconcentrated under reduced pressure. The residue was recrystallized fromchloroform-hexane to obtain the title compound (50.25 g, 85%) ascolorless needles.

Melting point: 152.8-154.0° C.

IR(KBr)cm⁻¹: 3250, 3053, 1677, 1597, 1541, 1456.

¹H-NMR (400 MHz, CDCl₃) δ: 2.43 (3H, s), 4.02 (2H, s), 4.42 (2H, q,J=7.9 Hz), 4.78 (2H, q, J=8.5 Hz), 6.47 (1H, s), 7.49 (1H, br s).

Elemental analysis for C₁₂H₁₁BrF₆N₂O₃:

Calculated: C, 33.90; H, 2.61; N, 6.59

Found: C, 34.13; H, 2.66; N, 6.65

(6) Preparation of2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide

To a mixed solution of1-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazinetritrifluoroacetate (4.00 g, 6.25 mmol) and potassium carbonate (4.32 g,31.26 mmol) in acetonitrile (100 mL) and water (30 mL),2-bromo-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide(2.20 g, 5.22 mmol) was added over 15 minutes under ice cooling andstirring. After stirring the reaction mixture at room temperature for 15hours, it was extracted with chloroform-water. The organic layer waswashed with brine, dried over anhydrous sodium sulfate, and concentratedunder reduced pressure. The residue was purified by columnchromatography (silica gel; 150 g; developer:hexane:acetone=Recrystallization was conducted from chloroform-hexane toobtain the title compound (3.04 g, 91%) as a pale yellow powder.

Melting point: 191-192° C.

IR(KBr)cm⁻¹: 3275, 1686, 1604, 1591, 1509.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.38 (3H, s), 2.42-2.62 (8H, m), 2.67 (2H,t, J=6.7 Hz), 3.30 (2H, s), 3.40 (2H, t, J=6.7 Hz), 4.82 (2H, q, J=8.8Hz), 4.90 (2H, q, J=8.8 Hz), 6.91 (1H, s), 7.47 (2H, m), 8.77 (1H, s),12.82 (1H, br s).

Elemental analysis for C₂₅H₂₆F₈N₆O₃S:

Calculated: C, 46.73; H, 4.08; N, 13.08

Found: C, 46.55; H, 4.12; N, 12.94

(7) Preparation of2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidehydrochloride

After dissolving2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide(1.00 g, 1.56 mmol) in ethanol (20 mL), pyridine hydrochloride (360 mg,3.12 mmol) was added. The reaction mixture was concentrated, and theresidue was recrystallized from ethanol to obtain the title compound(787 mg, 78%; including 40% equivalent of ethanol as determined by¹H-NMR) as a colorless crystalline powder.

(8) The crystalline powder (300 mg) prepared in the procedure (7) wassuspended in water (3 mL), followed by heating under reflux for 1 hour.After allowing the reaction mixture to cool down to room temperature,crystals were collected by filtration, washed with water (2 mL×2), andheated and dried at 50° C. for 7 hours under reduced pressure to obtainthe title compound (144 mg, 48%) in an ethanol-free form as a colorlesscrystalline powder.

FIG. 13 and FIG. 14 show the results of TG (thermogravimetricanalysis)-DTA (differential thermal analysis) measurements of2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

Melting point: 186-187° C.

IR(KBr)cm⁻¹: 3389, 3263, 1686, 1592, 1514, 1479, 1274.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.41 (3H, s), 2.80-3.74 (14H, m), 4.87 (2H,q, J=8.8 Hz), 4.94 (2H, q, J=9.0 Hz), 6.96 (1H, s), 7.50 (2H, t, J=9.0Hz), 9.11 (1H, br).

Elemental analysis for C₂₅H₂₇ClF₈N₆O₃S.1.6H₂O:

Calculated: C, 42.42; H, 4.30; N, 11.87; Cl, 5.01

Found: C, 42.72; H, 4.62; N, 11.23; Cl, 4.98

Example 3 Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride (1) Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide

In a procedure similar to that described in Example 2 except for the useof 1-[2-(benzimidazol-2-ylthio)ethyl]piperazine trihydrochloride inplace of 1-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazinetritrifluoroacetate, the title compound (91%) was obtained as acolorless crystalline powder.

Melting point: 152-153° C.

¹H-NMR (400 MHz, CDCl₃) δ: 2.43 (3H, s), 2.65-2.97 (8H, m), 3.01 (2H, t,J=5.0 Hz), 3.23 (2H, t, J=5.0 Hz), 3.31 (2H, s), 4.42 (2H, q, J=8.0 Hz),4.75 (2H, q, J=8.5 Hz), 6.48 (1H, s), 7.60-7.24 (2H, m), 7.41-7.65 (2H,m), 8.26 (1H, s).

(2) Preparation of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride

After dissolving the free base (1.00 g, 1.65 mmol) of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidein ethanol (20 mL), pyridine hydrochloride (381 mg, 3.30 mmol) wasadded. The reaction mixture was concentrated, and to the residue,ethanol (0.5 mL) and water (5 mL) were added.

A precipitate was collected by filtration to obtain2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidedihydrochloride (545 mg, 52%) as a colorless crystalline powder. Thedihydrochloride (250 mg) was suspended in water (2.5 mL), followed byheating to 80° C. to dissolve the same. After allowing the reactionmixture to cool down to room temperature, crystals were collected byfiltration, washed with water (1 mL×2), and heated and dried at 50° C.for 7 hours under reduced pressure to obtain the title compound (183 mg,73%) as a colorless crystalline powder.

FIG. 15 and FIG. 16 show the results of TG-DTA measurements of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its dihydrochloride, respectively.

Melting point: 153-154° C.

IR(KBrcm⁻¹): 3407, 1691, 1592, 1513, 1274, 1168.

¹H-NMR (400 MHz, CD₃CN) δ: 2.40 (3H, s), 2.90-3.19 (4H, m), 3.26 (2H,s), 3.27-3.42 (4H, m), 3.46 (2H, t, J=7.1 Hz), 3.81 (2H, t, J=7.1 Hz),4.57 (2H, q, J=8.3 Hz), 4.83 (2H, q, J=8.8 Hz), 6.71 (1H, s), 7.34 (2H,dd, J=3.2, 6.1 Hz), 7.64 (2H, dd, J=3.2, 6.1 Hz), 8.31 (1H, br).

Elemental analysis for C₂₅H₃₀Cl₂F₆N₆O₃S.1.3H₂O:

Calculated: C, 42.72; H, 4.67; N, 11.96; Cl, 10.09

Found: C, 42.73; H, 4.88; N, 11.86; Cl, 10.01

Example 4 Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride (1) Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide

By conducting a reaction and treatments similar to those described inExample 3 except for the use of1-[2-(benzoxazol-2-ylthio)ethyl]piperazine ditrifluoroacetate in placeof 1-[2-(benzimidazol-2-ylthio)ethyl]piperazine trihydrochloride, thetitle compound was obtained.

Melting point: 141-142° C.

¹HNMR (400 MHz, CDCl₃) δ: 2.42 (3H, s), 2.54-2.76 (8H, m), 2.84 (2H, t,J=6.9 Hz), 3.15 (2H, s), 3.49 (2H, t, J=6.9 Hz), 4.41 (2H, q, J=8.0 Hz),4.75 (2H, q, J=8.5 Hz), 6.46 (1H, s), 7.25-7.35 (2H, m), 7.43 (1H, d,J=7.8 Hz), 7.59 (1H, d, J=7.8 Hz), 8.38 (1H, s).

(2) Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride

After dissolving of2-[(4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide(1.00 g, 1.65 mmol) in ethanol (20 mL), pyridine hydrochloride (380 mg,3.29 mmol) was added. The reaction mixture was concentrated, and to theresidue, ethanol (0.5 mL) and water (5 mL) were added. A precipitate wascollected by filtration to obtain2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride (786 mg, 74%) as a colorless crystalline powder. Themonohydrochloride (300 mg) was suspended in water (1.5 mL), followed byheating to 80° C. to dissolve the same. After allowing the reactionmixture to cool down to room temperature, crystals were collected byfiltration, washed with water (0.5 mL×2), and heated and dried at 50° C.for 7 hours under reduced pressure to obtain the title compound (84 mg,28%) as a colorless crystalline powder.

FIG. 17 and FIG. 18 show the results of TG-DTA measurements of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

Melting point: 174-176° C.

IR(KBr)cm⁻¹: 3431, 1690, 1591, 1508, 1454, 1274, 1169, 1139.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.39 (3H, s), 2.66-3.82 (14H, m), 4.87 (2H,q, J=8.5 Hz), 4.94 (2H, q, J=9.0 Hz), 6.96 (1H, s), 7.33 (2H, t, J=3.4Hz), 7.60-7.69 (2H, m), 8.17 (1H, br).

Elemental analysis for C₂₅H₂₈ClF₆N₅O₄S.0.4H₂O:

Calculated: C, 46.11; H, 4.46; N, 10.75; Cl, 5.44.

Found: C, 46.17; H, 4.44; N, 10.74; Cl, 5.30.

Example 5 Preparation of2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride (1) Preparation of methyl2,6-dimethyl-4-trifluoromethylpyridine-3-carboxylate

1,1,1-Trifluoro-2,4-pentanedione (25.01 g, 135.3 mmol) was dissolved inacetonitrile (230 mL), followed by the addition of methyl3-aminocrotonate (15.57 g, 135.2 mmol). The mixture was subjected toheating under reflux for 20 hours. The reaction mixture was allowed tocool down to room temperature, and concentrated under reduced pressure.The residue was purified by column chromatography on silica gel (silicagel: 400 g; developer: hexane:acetone=10:1) to obtain the title compound(22.30 g, 71%) as a yellow oil.

(2) Preparation of 2,6-dimethyl-4-trifluoromethylpyridine-3-carboxylicacid hydrochloride

Methyl 2,6-dimethyl-4-trifluoromethylpyridine-3-carboxylate (23.30 g,99.9 mmol) was dissolved in ethanol (50 mL), followed by the addition of5 mol/L aqueous solution of potassium hydroxide (50 mL, 250 mmol). Themixture was subjected to heating under reflux for 2 days. The reactionmixture was allowed to cool down to room temperature, and concentratedhydrochloric acid (15 mL) was added and concentrated under reducedpressure. The residue was azeotropically distilled three times withethanol and toluene. The residue was suspended in ethanol under heat,and subsequent to filtration, the filtrate was concentrated underreduced pressure. The residue was azeotropically distilled twice withtoluene, and subsequent to the addition of ether, the reaction productwas collected by filtration to obtain the title compound (25.24 g, 99%)as a colorless powder.

(3) Preparation of3-tert-butoxycarbonylamino-2,6-dimethyl-4-trifluoromethylpyridine

2,6-Dimethyl-4-trifluoromethylpyridine-3-carboxylic acid hydrochloride(23.17 g, 90.6 mmol) was suspended in tert-butanol (175 mL), andsubsequent to the addition of Diphenylphosphorylazide (DPPA) (35.25 g,128.1 mmol) and triethylamine (31.36 g, 309.9 mmol), the suspension wassubjected to heating under reflux for 3 hours. Water (100 mL) was addedto the reaction mixture, followed by extraction from chloroform. Theorganic layer was dried over anhydrous sodium sulfate, and concentratedunder reduced pressure. The residue was purified by columnchromatography on silica gel (silica gel: 400 g; developer:hexane:acetone=10:1) to obtain the title compound (18.01 g, 68%) as apale yellow oil.

(4) Preparation of 3-amino-2,6-dimethyl-4-trifluoromethylpyridinedihydrochloride

3-tert-Butoxycarbonylamino-2,6-dimethyl-4-trifluoromethylpyridine (21.12g, 72.8 mmol) was dissolved in methanol (70 mL), and subsequent to theaddition of 10% hydrogen chloride in methanol (140 mL), the solution wasstirred at 60° C. for 12 hours. The reaction mixture was concentratedunder reduced pressure, and the residue was suspended in a mixture ofethyl acetate and ether. The reaction product was collected byfiltration, and washed with ether to obtain the title compound (15.64 g,82%) as a colorless powder.

(5) Preparation of2-bromo-N-(2,6-dimethyl-4-trifluoromethyl-3-pyridyl)acetamide

3-Amino-2,6-dimethyl-4-trifluoromethylpyridine dihydrochloride (15.60 g,59.30 mmol) was dissolved in methanol (100 mL). In an ice bath, anammonia-saturated methanol solution (300 mL) was added, and the mixturewas rendered uniform. The reaction mixture was extracted fromchloroform-water. The organic layer was washed with brine, dried overanhydrous sodium sulfate, and concentrated under reduced pressure. Theresidue was dissolved in dichloromethane (200 mL), and subsequent to theaddition of N,N-dimethylaniline (10.80 g, 89.12 mmol), a solution ofbromoacetyl bromide (15.52 g, 76.90 mmol) in dichloromethane (40 mL) wasadded dropwise while stirring the mixture in an ice bath. The mixturewas stirred at room temperature for two hours, and concentrated underreduced pressure. The residue was purified by column chromatography onsilica gel (silica gel: 400 g; developer: hexane:acetone=10:1→4:1→3:1).Recrystallization from ethyl acetate and hexane afforded the titlecompound (17.68 g, 96%) as colorless needles.

(6) Preparation of2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamide

The title compound was obtained as a free base by conducting a reactionand treatments similar to those described in Example 3 except that2-bromo-N-(2,6-dimethyl-4-trifluoromethyl-3-pyridyl)acetamide was usedin place of2-bromo-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand 1-[2-(benzothiazol-2-ylthio)ethyl]piperazine dihydrochloride wasused in lieu of 1-[2-(benzimidazol-2-ylthio)ethyl]piperazinetrihydrochloride.

(7) Preparation of2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride

2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamide(500 mg, 0.98 mmol) was dissolved in ethanol (10 mL), followed by theaddition of pyridine hydrochloride (227 mg, 1.96 mmol). The reactionmixture was concentrated, and to the residue, ethanol (0.2 mL) and water(2 mL) were added. A precipitate was collected by filtration to obtainthe title compound (295 mg, 55%) as a colorless crystalline powder.

FIG. 19 and FIG. 20 show the results of TG-DTA measurements of2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamideand its dihydrochloride, respectively.

Melting point: 221-212° C.

IR(KBr)cm⁻¹: 3427, 1692, 1430, 1389, 1240, 1177, 1154.

¹H-NMR (400 MHz, CD₃OD) δ: 2.68 (3H, s), 2.81 (3H, s), 3.32-3.45 (4H,m), 3.62-3.73 (6H, m), 3.82 (2H, t, J=6.6 Hz), 4.89 (2H, s), 7.37 (1H,dt, J=1.0, 8.1 Hz), 7.47 (1H, dt, J=1.0, 8.1 Hz), 7.85-7.93 (2H, m),8.26 (1H, s).

Elemental analysis for C₂₃H₂₈Cl₂F₃N₅OS₂.0.6H₂O:

Calculated: C, 46.56; H, 4.96; N, 11.80; Cl, 11.95

Found: C, 46.46; H, 5.07; N, 11.66; Cl, 12.04

Example 6 Preparation of2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride (1) Preparation of2-mercapto-5-trifluoromethylbenzoxazole

The title compound was obtained by conducting reactions and treatmentssimilar to those described in Example 85 of WO 98/54153 except for theuse of 4-trifluoromethylphenol in place of 2-trifluoromethylphenol.

(2) Preparation of1-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazineditrifluoroacetate

The title compound was obtained by conducting reactions and treatmentssimilar to those described in Example 22 of WO 98/54153 except for theuse of 2-mercapto-5-trifluorobenzoxazole in place of2-mercaptobenzoxazole.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.60-3.20 (10H, m), 3.57 (2H, t, J=6.7 Hz),7.61 (1H, d, J=8.6 Hz), 7.89 (1H, d, J=8.6 Hz), 8.04 (1H, s), 8.66 (2H,s).

(3) Preparation of2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide

The title compound was obtained as a colorless crystalline powder byconducting reactions and treatments similar to those described inExample 24 of WO 98/54153 except for the use of1-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazineditrifluoroacetate in place of1-[2-(benzoxazol-2-ylthio)ethyl]piperazine ditrifluoroacetate.

Melting point: 103-104° C.

¹H-NMR (400 MHz, CDCl₃) δ: 2.42 (3H, s), 2.49 (3H, s), 2.52 (3H, s),2.60-2.82 (8H, m), 2.86 (2H, t, J=6.8 Hz), 3.21 (2H, s), 3.51 (2H, t,J=6.8 Hz), 6.67 (1H, s), 7.51-7.53 (2H, m), 7.85 (1H, s), 8.55 (1H, s).

(4) Preparation of2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride

2-[4-[2-(5-Trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide(200 mg, 0.35 mmol) was dissolved in ethanol (4 mL), followed by theaddition of pyridine hydrochloride (82 mg, 0.70 mmol). The reactionmixture was concentrated, and to the residue, ethanol (0.5 mL) and water(5 mL) were added. A precipitate was collected by filtration to obtainthe title compound (180 mg, 85%) as a colorless crystalline powder.

FIG. 21 and FIG. 22 show the results of TG-DTA measurements of2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

Melting point: 195-196° C.

IR(KBr)cm⁻¹: 3427, 1685, 1501, 1437, 1327, 1143, 1123.

¹H-NMR (400 MHz, DMSO-d₆) δ: 2.42 (3H, s), 2.43 (3H, s), 2.46 (3H, s),2.70-3.84 (14H, m), 6.94 (1H, s), 7.72 (1H, d, J=8.3 Hz), 7.91 (1H, d,J=8.3 Hz), 8.06 (1H, s).

Elemental analysis for C₂₄H₂₉ClF₃N₅O₂S₃.0.5H₂O:

Calculated: C, 46.71; H, 4.90; N, 11.35

Found: C, 46.67; H, 4.89; N, 11.33

Example 7 Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride (1) Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide

The title compound was obtained by conducting a reaction and treatmentssimilar to those described in the procedure (1) of Example 3 except that2-bromo-N-[2-(2-methoxyethoxy)-6-methyl-4-(2,2,2-trifluoroethoxy)-3-pyridyl]acetamidewas used in place of2-bromo-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand 1-[2-(benzoxazol-2-ylthio)ethyl]piperazine dihydrochloride was usedin lieu of 1-[2-(benzimidazol-2-ylthio)ethyl]piperazinetrihydrochloride.

(2) Preparation of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride

2-[4-[2-(Benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide(500 mg, 0.86 mmol) was dissolved in ethanol (10 mL), followed by theaddition of pyridine hydrochloride (198 mg, 1.71 mmol). The reactionmixture was concentrated, and to the residue, ethanol (0.2 mL) and water(2 mL) were added. A precipitate was collected by filtration to affordthe title compound (134 mg, 25.2%) as a colorless crystalline powder.

FIG. 23 and FIG. 24 show the results of TG-DTA measurements of2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamideand its monohydrochloride, respectively.

Melting point: 181-182° C.

IR(KBr)cm⁻¹: 3432, 1686, 1593, 1507, 1454, 1170, 1137.

¹H-NMR (400 MHz, CD₃CN) δ: 2.38 (3H, s), 2.92-3.26 (8H, m), 3.31 (3H,s), 3.42-3.59 (4H, m), 3.62 (2H, t, J=4.9 Hz), 3.72-3.84 (2H, m), 4.38(2H, t, J=4.9 Hz), 4.54 (2H, q, J=8.3 Hz), 6.61 (1H, s), 7.28-7.36 (2H,m), 7.54 (2H, dd, J=2.2, 5.6 Hz), 8.19 (1H, br).

Elemental analysis for C₂₆H₃₃ClF₃N₅O₅S.0.4H₂O

Calculated: C, 49.78; H, 5.43; N, 11.16; Cl, 5.65

Found: C, 49.76; H, 5.31; N, 11.25; Cl, 5.78

1-15. (canceled)
 16. A method for preparing an acid addition salt of apiperazine derivative represented by the following formula (1) or awater adduct of said acid addition salt, which is characterized byreacting the piperazine derivative with an acid salt of pyridine,wherein formula (1) is:

wherein X represents an oxygen atom or a sulfur atom, Y¹, Y² and Y³ eachindependently represent a hydrogen or halogen atom or a lower alkyl orlower haloalkyl group, R¹, R² and R³ each independently represents ahydrogen or halogen atom or a lower alkyl, lower haloalkyl, loweralkylthio, lower haloalkoxy or lower alkoxyalkoxy group, l denotes aninteger of from 1 to 2, m denotes an integer of from 2 to 4, and ndenotes an integer of from 1 to
 3. 17. The method for preparing an acidaddition salt of a piperazine derivative described in claim 16, whereinsaid piperazine derivative is represented by the following formula (2):

wherein X represent an oxygen atom or a sulfur atom, Y¹ and Y² eachindependently represents a hydrogen or halogen atom or a trifluoromethylgroup, R¹ and R² each independently represent a methyl, trifluoromethyl,methylthio, trifluoroethoxy or methoxyethoxy group.
 18. The method ofpreparing an acid addition salt of a piperazine derivative or wateradduct of said acid addition salt described in claim 16, wherein saidpiperazine derivative is:2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,or2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide.19. The method of claim 16, wherein said piperazine derivative is:2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamide.20. The method of preparing an acid addition salt of a piperazinederivative or water adduct of said acid addition salt described in claim16, wherein the acid in said acid salt of pyridine is selected from thegroup consisting of hydrochloric acid, sulfuric acid, nitric acid,phosphoric acid, sulfurous acid, nitrous acid, hydrobromic acid,hydroiodic acid, acetic acid, butyric acid, stearic acid, oxalic acid,maleic acid, succinic acid, fumaric acid, citric acid, lactic acid,tartaric acid, malic acid, mandelic acid, salicylic acid, pamoic acid,pantothenic acid, gluconic acid, ethanedisulfonic acid, benzenesulfonicacid, paratoluenesulfonic acid, methanesulfonic acid, glutamic acid,aspartic acid, trifluoroacetic acid, and tannic acid.
 21. The method ofpreparing an acid addition salt of a piperazine derivative or wateradduct of said acid addition salt described in claim 16, wherein saidacid salt of pyridine is a pyridine hydrochloride.
 22. The method ofpreparing an acid addition salt of a piperazine derivative or wateradduct of said acid addition salt described in claim 16, wherein saidpolyacidic basic compound is:2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamide,or2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamide;and said acid salt of pyridine is a pyridine hydrochloride.
 23. Themethod of preparing an acid addition salt of a piperazine derivative orwater adduct of said acid addition salt described in claim 16, whereinsaid polyacidic basic compound is:2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamide;and said acid salt of pyridine is a pyridine hydrochloride.
 24. Acompound that can be made by the process of claim 16, selected from thegroup consisting of:2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, and2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof.
 25. A compound that can bemade by the process of claim 16 selected from the group consisting of:2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride crystal or a water adduct thereof,2-[4-[2-(5-trifluoromethylbenzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride crystal or a water adduct thereof, and2-[4-[2-(benzoxazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2-(2-methoxyethoxy)-4-(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride crystal or a water adduct thereof.
 26. A compound thatcan be made by the process of claim 16 comprising2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride or a water adduct thereof.
 27. A compound that can bemade by the process of claim 16 comprising2-[4-[2-(benzothiazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,6-dimethyl-4-trifluoromethyl-3-pyridyl]acetamidedihydrochloride crystal or a water adduct thereof.
 28. Amonohydrochloride of a piperazine derivative represented by formula (2):

wherein X represents —NH—, Y¹ and Y² each independently represent ahydrogen or halogen atom or a trifluoromethyl group, and R¹ and R² eachindependently represent a methyl, trifluoromethyl, methylthio,trifluoroethoxy or methoxyethoxy group.
 29. The monohydrochloride of thecompound of claim 28, which comprises formula (2):

wherein X represents —NH, Y¹ and Y² each independently represent ahydrogen or halogen atom or a trifluoromethyl group, and R¹ and R² eachindependently represent a methyl, trifluoromethyl, methylthio,trifluoroethoxy or methoxyethoxy group.
 30. The monohydrochloride ofclaim 28, which is selected from the group consisting of:2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof, and2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride or a water adduct thereof.
 31. The monohydrochlorideof claim 28, which is selected from the group consisting of:2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride crystal or a water adduct thereof, and2-[4-[2-(5,6-difluorobenzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(2,2,2-trifluoroethoxy)-6-methyl-3-pyridyl]acetamidemonohydrochloride crystal or a water adduct thereof.
 32. Themonohydrochloride of claim 28 that is a 0.9 water adduct of2-[4-[2-(benzimidazol-2-ylthio)ethyl]piperazin-1-yl]-N-[2,4-bis(methylthio)-6-methyl-3-pyridyl]acetamidemonohydrochloride.
 33. A pharmaceutical composition comprising themonohydrochloride of claim 28.